Scores of armed police were surrounding the gunmen behind the massacre after they were traced to an address near Paris.

Dammartin-en-Goele, 25 miles north-east of the capital, was sealed off as a siege situation developed amid reports that brothers Said and Cherif Kouachi may have taken hostages.

Officials denied reports of fatalities after shots were fired during the operation.

The brothers were cornered in the premises of a construction firm after stealing a car earlier.

Officers from the GIGN special forces unit were said to have begun negotiations with the Islamic fanatics, who are believed to have murdered 12 people at the offices of the satirical magazine on Wednesday.